Multiple regulated supply voltages are needed in many electronic applications, which require different supply voltages for different function modules. They are also needed in implementing dynamic voltage scaling techniques to effectively reduce the power consumption of a system. Possible applications include personal digital assistants (PDAs), notebook computers, System-on-a-Chips (SoCs) for signal processing, microprocessors, power amplifiers for 3G W-CDMA transceivers and ADSLs, and so on. Among existing multiple-supply implementations, a single-inductor multiple-output (SIMO) switching converter is a very cost-effective solution. SIMO converters require only one off-chip inductor and fewer on-chip power switches that help reduce system volume and save chip area. In addition, they are helpful in reducing EMI and cross couplings due to the presence of inductors and transformers, since the number of these magnetic components has been reduced to one.
However, existing SIMO converters either work in a continuous conduction mode (CCM) or discontinuous conduction mode (DCM). A CCM SIMO converter suffers from cross-regulation problems from having possible negative inductor current at light loads and hence low efficiency. A DCM SIMO converter has large peak inductor current and current ripple at heavy loads. This leads to large switching noise and imposes enormous current stress on the system.
It would be desirable to develop a new working mode for a SIMO switching converter, which not only inherits the merits of a DCM SIMO converter in suppressing cross regulation, but also is capable of handling large current stress at heavy loads. In addition, it is preferred to implement this working mode with very few components, because too many additional components would decrease the efficiency and increase the cost and volume of the system.
It would also be desirable that the design can be flexibly extended to have single or multiple outputs and for converters with different DC-DC conversion types such as the buck, boost and flyback converters for different application requirements.